Improve attribute list syntax suggestion

[pickfire]

Given the following code:

#[doc(alias = ["foo"])]
fn t() {}

The current output is:

   Compiling playground v0.0.1 (/playground)
error: expected unsuffixed literal or identifier, found `[`
 --> src/lib.rs:1:15
  |
1 | #[doc(alias = ["foo"])]
  |               ^

error: aborting due to previous error

error: could not compile `playground`

Ideally the output should look like:

   Compiling playground v0.0.1 (/playground)
error: expected unsuffixed literal or identifier, found `[`
 --> src/lib.rs:1:15
  |
1 | #[doc(alias("foo"))]
  |               ^

error: aborting due to previous error
help: list syntax is not supported for `alias` attribute
suggestion: use `alias("foo")` instead of `alias = ["foo"]`

error: could not compile `playground`

https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=dcc601d35deecf1558b3dd66660bf8d5

Follow up of #82846

[pickfire]

Just saw this in the wild.

    #[clap(aliases = &["baz", "fizz"])]

But clap aliases rather than doc aliases. https://github.com/clap-rs/clap/blob/6ce1e4fda211a7373ce7c4167964e6ca073bdfc1/clap_derive/examples/subcommand_aliases.rs#L13

So it is still possible someone might try this.